Thromb Haemost 2020; 120(11): 1512-1523
DOI: 10.1055/s-0040-1715441
Coagulation and Fibrinolysis

Evolutionary Adaptations in Pseudonaja Textilis Venom Factor X Induce Zymogen Activity and Resistance to the Intrinsic Tenase Complex

Mark Schreuder*
1  Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
,
Geraldine Poenou*
1  Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
2  AP–HP, Hôpital Louis Mourier, Colombes, France
,
Viola J. F. Strijbis
1  Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
,
Ka Lei Cheung
1  Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
,
Pieter H. Reitsma
1  Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
,
Mettine H. A. Bos
1  Division of Thrombosis and Hemostasis, Einthoven Laboratory for Vascular and Regenerative Medicine, Leiden University Medical Center, Leiden, The Netherlands
› Author Affiliations
Funding This work was financially supported by the Bayer Hemophilia Awards Program (Special Project Award) and Landsteiner Foundation for Blood Transfusion (LSBR, grant. no. 1451). The funding agencies had no role in the preparation, review, or approval of the manuscript.

Abstract

The venom of the Australian snake Pseudonaja textilis comprises powerful prothrombin activators consisting of factor X (v-ptFX)- and factor V-like proteins. While all vertebrate liver-expressed factor X (FX) homologs, including that of P. textilis, comprise an activation peptide of approximately 45 to 65 residues, the activation peptide of v-ptFX is significantly shortened to 27 residues. In this study, we demonstrate that exchanging the human FX activation peptide for the snake venom ortholog impedes proteolytic cleavage by the intrinsic factor VIIIa–factor IXa tenase complex. Furthermore, our findings indicate that the human FX activation peptide comprises an essential binding site for the intrinsic tenase complex. Conversely, incorporation of FX into the extrinsic tissue factor–factor VIIa tenase complex is completely dependent on exosite-mediated interactions. Remarkably, the shortened activation peptide allows for factor V-dependent prothrombin conversion while in the zymogen state. This indicates that the active site of FX molecules comprising the v-ptFX activation peptide partially matures upon assembly into a premature prothrombinase complex. Taken together, the shortened activation peptide is one of the remarkable characteristics of v-ptFX that has been modified from its original form, thereby transforming FX into a powerful procoagulant protein. Moreover, these results shed new light on the structural requirements for serine protease activation and indicate that catalytic activity can be obtained without formation of the characteristic Ile16–Asp194 salt bridge via modification of the activation peptide.

Authors' Contributions

M.S., G.P., and M.H.A.B. designed the research; M.S., G.P., V.J.F.S., and K.L.C. performed the experiments. M.S., G.P., V.J.F.S., K.L.C., P.H.R., and M.H.A.B. analyzed the data; M.S. wrote the manuscript; P.H.R. and M.H.A.B. reviewed and revised the manuscript.


* Co-first authors.


Supplementary Material



Publication History

Received: 18 February 2020

Accepted: 25 June 2020

Publication Date:
20 August 2020 (online)

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